1. Field of the Invention
The present disclosure relates to digital recording apparatus, and more particularly, to digital data coding apparatus and digital versatile disk (DVD) recording apparatus capable of reducing the number of times a memory device is accessed in order to code digital data to be recorded on a DVD device.
2. Description of the Related Art
A DVD system generally processes data in units of data sectors, including an error correction code (ECC) block. The ECC block facilitates mass data transmission without errors.
Each data sector includes 12 rows of 172 bytes. A first field of the data sector includes ID data, IED data, and CPR_MAI data, and a last field of the data sector includes an error detection code (EDC). An ECC block of a DVD includes an information field having the data sector, 10 bytes of parity in (PI) parity, and 16 rows of parity out (PO) parity used to correct data errors of the information field.
FIG. 1 illustrates the structure of a data sector 100 to be recorded on a DVD. Referring to FIG. 1, user data or main data to be recorded on the DVD from a host computer are classified in units of 2048 bytes. The data sector 100 comprises 4 bytes of ID data indicating address information for each data sector and sector power, 2 bytes of IED data that is an EDC of the ID data, and 6 bytes of CPR_MAI data indicating a reserve field or copyright management information. A first row of the data sector 100 includes 160 bytes of main data D0 through D159. Each of second through eleventh rows includes 172 bytes of main data and a twelfth row includes 168 bytes of main data D1880 through D2047 and 4 bytes of EDC data. Each data sector consists of 2064 bytes (2048 bytes+16 bytes), that is, twelve 172-byte rows.
FIG. 2 illustrates the structure of an ECC block 200 comprising a plurality of the data sectors 100 shown in FIG. 1. Referring to FIG. 2, the ECC block 200 contains sixteen of the data sectors 100 to which ECC is added by calculating a Reed-Solomon code. The ECC block is recorded on the DVD to maintain data reliability. The ECC block is formed by calculating a Reed-Solomon code of one block that is formed from 16 data sectors and adding ECC.
The ECC block includes 10 bytes of ECC calculated from each row of the 16 data sectors in a horizontal direction, and the calculated ECC is added to the back of each corresponding row. A column of the added ECC forms a PI parity block having a size of 10 bytes×192 rows. The ECC block further includes 16 bytes of ECC calculated from each column of the data sectors and the PI parity block, and the calculated ECC is added in a vertical direction to the bottom of each corresponding column. The row of the added ECC forms a PO parity block having a size of (172+10) bytes×16 rows. Therefore, one digital data block to be recorded on the DVD is 182 bytes×208 rows=37,856 bytes.
An external memory device for temporarily storing data is required to process a signal used to code and modulate main data transmitted from a host computer. SDRAM is used as the external memory device. An integrated circuit (IC) is used for coding data to be recorded to the DVD. The IC must frequently access the SDRAM in order to store the data into the SDRAM, and in order to read and process the stored data to be recorded to the DVD.
FIG. 3 is a diagram illustrating a process of accessing external memory in a conventional DVD recording apparatus. Referring to FIG. 3, a recording apparatus 300 for recording digital data to a DVD includes a DVD recorder IC 301 and external memory or SDRAM 303. Main data transmitted from a host computer are stored in the SDRAM 303 at step 305. The DVD recorder IC 301 accesses the SDRAM 303 32,768 times (2048×16 sectors) per data block.
The main data stored in the SDRAM 303 are read and ECC encoded at step 307. The number of times when the SDRAM 303 is accessed is 2048×16 sectors=32,768 times per data block at step 307, which is equal to the number of times for storing the main data. The DVD recorder IC 301 adds 4 bytes of ID data, 2 bytes of IED data, and 6 bytes of CPR_MAI data to each data sector, performs an EDC operation and adds the EDC. Each data sector contains 2064 bytes including 16 bytes of additional information added to 2048 bytes of main data. Thereafter, the data is scrambled. The scrambled data are ECC encoded in data block units by adding 10 bytes of PI parity to each row and adding 16 rows of PO parity to the block containing the PI parity. (10×192) bytes of PI parity and (182×16) bytes of PO parity are added as shown in FIG. 2. Thus, one data block contains 182 bytes×208 rows=37,856 bytes.
The encoded data are stored in the SDRAM 303 at step 309. At this time, the DVD recorder IC 301 accesses the SDRAM 303 37,856 times per data block.
The DVD recorder IC 301 reads the data stored in the SDRAM 303 to perform eight-to-fourteen modulation (EFM) at step 311. At this time, the DVD recorder IC 301 accesses the SDRAM 303 37,856 times per data block.
The DVD recorder IC 301 performs the EFM for the read data and records the modulated data on the DVD. Digital data are recorded on the DVD at a predetermined speed. The DVD recorder IC 301 must read and store data in the SDRAM 303, which is an external buffer memory, within a designated time.
However, as DVD recording apparatuses record data at higher speeds, the rate at which data is to be accessed from the external buffer memory must be increased. Therefore, when mass data are recorded on a DVD-RAM at high speed, it is important to reduce the number of times the external buffer memory is accessed with a disk recording speed of high transmission rate.